This invention relates to an electronic weigher such as a counting scale, weighing scale or fee scale. More particularly, the invention relates to an electronic weigher adapted so as to be able to sense a problem in amplification circuitry extending from the input side of an operational amplifier for amplifying a weight signal to the output side of an A/D converter.
An electronic weigher is susceptible to a variety of troubles. Since a failure which may develop in the amplifier circuitry of such a weigher cannot be ascertained externally of the weigher, there is the danger that a weighing error outside allowable limits may occur without being noticed, thereby resulting in use of an erronous reading. For this reason, the prior-art practice is to load the weigher with a test weight from time to time and then examine the weight reading to determine if the weigher is operating normally. However, it is very troublesome for the user to examine the weigher every day by application of the test weight. Hence there is need of an improvement in this area.